The intermittent slews are still a concern for when you return from the eclipse trip so, while this is all fresh in my mind, I'd prefer to address these problems now so these thoughts are here when you get back to this after the eclipse.
Last night, while I should have been sleeping, the more I thought about my own slewing problems I had way back when I'm remembering all the frustration I had in trying to figure out my intermittent slewing problem. I had a new Talentcell, including cables I purchased separately, as well as an AC adapter I was using with a previous mount. I had intermittent slewing for days. Sometimes it slewed properly. Sometimes it didn't do anything. Other times it would only slew part of the way to the target. I always heard that faint crackle sound of the motors make while tracking so no complete loss of power. Although, when the slew stopped in mid-slew, I often would have to shut down and boot up again. The times I didn't have to shut down, however, I would still need to reboot to get the motor counts back to zero. At the time, whenever I had to freezing in mid-slew problem, I was thinking I just needed a reboot because I would need one to reset the motor counts anyway but the more logical thing is the mount crashed due to an intermittent power issue/arcing inside the cable or at the jack.
After a few days of this intermittent problem, I finally thought to try my AC power adapter which has its own cable. I had no problems while using AC power so I ordered a new 5.5mm x 2.1mm cable from a different supplier. The Talentcell worked fine on a larger mount (5.5mm x 2.5mm) so I assumed the Talentcell was good. When the new cable arrived, I no longer had intermittent problems with slewing.
In my case, I had a new cable that was defective somehow. Since it seems that your settings are correct in ASCOM, this would be the next logical thing to check.
That being said, let's revisit the ASCOM settings. I pulled out my laptop to actually step through setup in both Device Hub and POTH so I could write down the exact steps. I'll type that down below after I close this comment.
Now, there are still settings in each piece of software that you connect to the Hub that must be correct too. I think you'll understand why I'm not going to go through that exercise. We won't necessarily even been using the same pieces of software either. This does remind me of something though....
Another problem I experienced with an older mount before I had the iEXOS-100 (so pre-2019) was with ASCOM. I downloaded and installed ASCOM, ran ASCOM DIagnostics, everything checked out fine. I had all sorts of problems. I troubleshooted this problem with the ES engineer for days until he finally recommended I uninstalled ASCOM and re-install. I did that.. same problems. I uninstalled and re-installed one more time... everything was then working as expected. So there is this possibility too.
Hmmm... since this problem of intermittent slews happens in both ASCOM serial as well as wirelessly in ExploreStars, that probably eliminates a possible problem with the ASCOM install. Which also means it is probably not caused by a bad USB serial cable (USB-A to USB-mini cable with no FTDI chipset in it). That leaves the only common denominator as the power cable, the Talentcell and/or the power jack on the mount.
Hmmm... power save settings on the computer/tablet you are using could create problems too. Make sure you have shut off all power saving features. Also, make sure screensavers are turned off. And, the next time you experience the intermittent slew problem when wirelessly connected to ExploreStars, go back to Internet Settings to ensure you are actually still connected to the mount. Some devices like to drop a non-internet WiFi connection when a WiFi connection is available. Obviously, this is irrelevant when connected to ASCOM through serial but Power Saving features could affect USB ports (possibly, I think) as well as WiFi. That is something to check too.
Patrick
So, the setup for Device Hub...
Tools --> Setup --> Choose --> ES PMC8 Telescope (in the drop-down menu)
Click "Properties"
Select "iEXOS-100" in drop-down
Select radio button "Enable Serial Port"
Select appropriate tracking rate in the drop-down menu
Go the "Site Data" tab and input all your specific data
Click "OK"
Click "OK"
Click "OK"
Click "Connect Telescope"
The setup for POTH...
Click "Setup"
in the next window also click "Setup"
Then input all data and info mentioned in the Device Hub steps above
Click "OK"
Make sure site information is correct in this POTH window
Click "Connect"
then click "Okay" to go back to the first small POTH window
Some 3rd party software also will require you to input all of or some of this data in their setup so make sure you find all hidden places to input info in the software too. I think all recently updated software probably just reads this info from ASCOM. Older programs like CdC may require all the info in their setup.
Lastly, if you do still have problems when you have more time to address this after exhausting everything I suggested, THE place to be looking for help is in the ESPMC-Eight groups io. There will be far more eyes on your problem there and there are about a dozen people in there who can troubleshoot more effectively because they wrote some of the software/driver/help_files/manuals/etc and they know the mount hardware inside and out.